20-story Building Research Articles

Seismic evaluation and retrofit of reinforced concrete structures

The destructive earthquakes in the world clearly reveal the importance of the seismic behavior of the structures. The current study proposes and numerically investigates a systematic technique for the seismic assessment and retrofit of reinforced-concrete buildings according to both material strain limit approach and Quadrants assessment method. In this study numerical analysis were made for two three-dimensional building models, namely a single-storey 30 years old existing RC building in Koyna-Warna area (Zone-IV) in India, and an earthquake-resistant designed 4-story RC building. The structural analyses were performed for two 3-D models of the selected buildings are analysed. Nonlinear static adaptive pushover analysis method was used in Seismostruct software program for two different buildings. While one of the buildings is an existing building, the other is chosen as a new building. Structural characteristics and deficiencies of the investigated single-storey existing reinforced-concrete structure necessitated seismic evaluation. The deficiencies include pitched roofs, re-entrant corners, and structural distress such as structural element cracking and cover concrete spalling, among others. The single-story RC building is retrofitted with RC jacketing and fiber-reinforced polymer sheet wrapping, while the four-storey RC building does not need to be retrofitted based on the Quadrants assessment method. Also, the significant seismic design parameters are evaluated before and after the retrofit. The results show that the material strain limit technique when combined with the Quadrants assessment method makes a more efficient technique for seismic assessment and retrofit purpose. Also, the ultimate capacity and over strength factor of the retrofitted single-storey RC existing building are found 2.04 times and 1.82 times increased in X and Y direction as compared to the building without retrofit, because of the RC jacketing and FRP sheet wrapping.

Tuning of a Viscous Inerter Damper: How to Achieve Resonant Damping Without a Damper Resonance

Inerter dampers are effectively employed to mitigate and dampen structural vibrations in slender or high-rise buildings. The simple viscous inerter damper, with a viscous dashpot placed in series with an inerter, is designed to create resonant vibration damping, although the damper itself is without an internal resonance. The apparent resonant behavior is instead obtained by increasing the damper inertance until the two lowest modes of the considered building model interact, whereafter the viscous coefficient is adjusted until the desired response mitigation is achieved. The present modal interaction tuning requires that the reduced-order single-mode dynamic model of the building includes both inertia and flexibility from the (other) modes otherwise discarded by the model reduction. While the inertia correction adjusts the modal mass of the inerter damper, the corresponding flexibility introduces the apparent damper stiffness that creates the desired damper resonance. Thus, the accurate representation of other modes is essential for the design and resonant tuning of the simple viscous inerter damper. The resonant damper performance by the non-resonant viscous inerter damper is illustrated by a numerical example with a 20-story building model, for which the desired resonant modal interaction requires an inertance of almost ten times the entire translational building mass.

ДОСЛІДЖЕННЯ ЕКОНОМІЇ ЕНЕРГЕТИЧНИХ І ВОДНИХ РЕСУРСІВ В СИСТЕМІ ВОДОПОСТАЧАННЯ БАГАТОПОВЕРХОВОГО БУДИНКУ ЗА ДВОРІВНЕВИХ СТОЯКІВ

The influence of the structure of the electromechanical water supply system of a 12-story building (replacing one riser with two risers of different levels) on the efficiency of energy and water resource use was studied. A mathematical model of the electromechanical system has been developed and implemented in software, which takes into account the dependence of the floor consumption on the pressure value and allows determining the water needs of consumers based on the given cyclorama of the water consumption of the house. According to the information about the known parameters of the basic version of the water supply system, the parameters of one floor and the parameters of the variants of the building system with risers for servicing floors are determined: 1-12; 1-6; 7-12. The study was carried out taking into account the proposed time dependence of the change in the input pressure of the house. Means of generalized determination of the energy efficiency of the asynchronous motor of the water supply system based on approximate dependences of nominal efficiency on power and efficiency on the degree of loading have been developed. The comparison of options was carried out according to the formulated expression of the efficiency criterion, as the ratio of the daily useful effect of the water supply system to consumers to the cost of electricity and water consumed during the given period. According to the simulation results, the two riser option provides savings of 4% of water and 25% of electricity with their ratio in monetary terms 6:1. This justifies the priority of taking into account water savings when justifying the modernization of water supply systems (parallel zoning, adjustable electric drive). References 11, table 1, figures 3.

Effect of applying phase change materials (PCM) in building facades on reducing energy consumption

Since fossil fuels are limited and there is an increasing demand for energy consumption, energy conservation and reducing consumption have become significant challenges. Applying phase change materials (PCM) for latent thermal energy storage (TES) systems is an effective method for energy conservation that has been widely considered in recent years. The building facade has the highest capacity for conserving or wasting energy due to its vast exposure to the environment. As a result, a change in attitude toward designing and constructing facades is considered a necessity since it is one of the key elements of building design. One approach to prevent materials from leaching from a structure where PCMs are incorporated is encapsulating and blending them with a suitable polymer. Choosing a PCM with suitable melting temperature, a polymer compatible with this material as a preserver and the best percentage of PCM in the polymer are key components. In this paper, the goal has been investigated through a 2-step process, including experimental and simulation phases. First, the effect of polyethylene glycol (PEG) as the PCM in the mixture with poly methyl methacrylate (PMMA) for heat protection has been studied. Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) measurement techniques were employed to study and determine the melting points of the samples and the mixed substructures. The results show that the best percentage for PEG in this research is 60%. In the second phase, to study the effect of polymers carrying the PCMs on the building’s energy consumption, a 5-story building with PCMs applied to its facade was simulated in EnergyPlus software. The annual heating and cooling loads of the building in each situation were then calculated. The results of the simulation and modeling shows that applying the PCMs will ultimately lead to a 40% decrease in heating load and 15% decrease in cooling load of the building.

Seismic Observation of Piled Raft Foundation Supporting a 10-Story RC Residential Building Adjacent to a Pile Foundation Building

Seismic Observation of Piled Raft Foundation Supporting a 10-Story RC Residential Building Adjacent to a Pile Foundation Building

Shake-Table Test of a Seismically Resilient 10-Story Mass Timber Building with Supplemental Uplift Friction Dampers

Shake-Table Test of a Seismically Resilient 10-Story Mass Timber Building with Supplemental Uplift Friction Dampers

Pushover Analysis of a Reinforced Cement Concrete (RCC) Structure Incorporating Fibre-Reinforced Polymers to Address Vertical Irregularities

India has had four of the world's most destructive earthquakes in the past ten years, and our country is often rocked by earthquakes of low to moderate intensity. Since many buildings were severely damaged or collapsed, it has sparked debate whether framed constructions are sufficiently sturdy to withstand significant vibrations. As a result, the strength or ability of existing reinforced concrete structures to withstand seismic loads can be evaluated. The performance level of earthquake-prone buildings is evaluated using a performance-based design. One seismic technique for assessing a building's performance level is push-over analysis. It is possible to determine whether damage occurs at the member or structure level using pushover analysis. The study employs pushover analysis by Applied Technology Council (ATC) – 4), a seismic assessment technique, to evaluate the ability of 20-story buildings in seismic Zone III (with hard soil characteristics) to resist earthquake-induced forces. The primary objective was to assess the performance of structures reinforced with different fiber-reinforced polymer (FRP) materials, including aramid, glass, and carbon fibers, known for their high flexibility and strength in seismically active regions. To determine the best fiber-reinforced polymer configuration, the study considers the following parameters: pushover curve, target displacement, story shear, time period, maximum story displacement, and story drift based on pushover analysis independently. Through the pushover analysis method, the research discovers that FRP wrapping can significantly improve the seismic performance of reinforced concrete buildings. The findings aim to improve building design practices by recommending fiber-reinforced polymer configurations for better earthquake resistance, ensuring that future constructions are better equipped to handle seismic activity.

Enhancing the seismic stability of buckling-restrained steel braced frames in subduction interface seismic regions using viscoelastic dampers

This article proposes a stability-enhanced alternative to traditional buckling-restrained steel braced frames (BRBFs) for application in tall-rise steel buildings located in high seismic regions. The viscoelastic (VE)-BRBF is a BRBF featuring V or inverted-V bracing configurations and integrates vertically aligned VE dampers at beam–brace intersections on each story. The incorporation of VE dampers addresses two significant drawbacks of traditional BRBFs. First, it enhances the post-elastic lateral story shear stiffness, crucial for mitigating P-delta-induced inelastic drift concentrations and global instability, particularly under subduction interface events. Second, it augments inherent damping, a parameter typically low in conventional steel buildings. These improvements alleviate the need for the stability-related stringent height limitations imposed by design codes, such as the 40 m limit for SC4 buildings in Canada. Utilizing nonlinear response history analysis, the seismic stability performance of the proposed system is assessed against traditional BRBFs designed with classical strength amplification through an inelastic stability coefficient. The assessment is conducted on 10- and 20-story steel buildings in Vancouver, BC, considering seismic excitations involving the subduction interface. The results demonstrate that traditional BRBF designed overlooking height limitations failed to meet design code acceptance criteria, with several stability cases exhibiting global instability and excessive drifting. In contrast, the incorporation of VE dampers in the VE-BRBF demonstrated responses that met the design code acceptance criteria, with uniform drift distributions and mitigated P-delta effects and with residual post-earthquake drifts within repair limits, regardless of building height or seismic excitation type.

Characterizing Effective Supplemental Damping Properties to Estimate the Seismic Response of Non-Proportionally Damped Two-Way Asymmetrical Buildings

ABSTRACT Building codes stipulate that design response spectra can be reduced when the damping ratio of the concerned building exceeds 5%. To reduce the 5%-damped design response spectrum, it is necessary to quantify the effective damping of non-proportionally damped buildings. It is recognized that not only the resultant damping but also the distribution characteristic of viscous dampers across the floors of a building affects the seismic response of asymmetric-plan buildings. For this reason, this study proposes a method to characterize the effective damping properties of non-proportionally damped two-way asymmetric-plan buildings. The proposed method involves constructing a non-proportionally damped three-degree-of-freedom (3DOF) oscillator in modal space. This modal oscillator reflects the characteristic of the dominant mode in each of the three directions of the two-way asymmetric-plan building. By mapping the seismic response of the 3DOF oscillator into physical space, the seismic response of a 20-story example building was satisfactorily estimated. This study also examines the effectiveness of using code-stipulated effective damping in estimating the seismic response of the example building.

The Impact of an Office Fire Combined with the Stack Effect in a Multi-Story Building

The current study was based on two simulations conducted in FDS that examined the influences of an office fire on the ground floor of a 10-story building (with 9 above-ground floors) and its impact on air and smoke flow. After reviewing the literature, we observe a significant gap in current research addressing the dynamic interdependence between fire development and the stack effect in multi-story residential buildings. It was found that the fire significantly intensified the stack effect, increasing the temperature in the stairwell, particularly on the ground floor. Gas velocities within the building increased but do not endanger the lives of the occupants. Visibility remained sufficient for evacuation from the apartments, except in critical areas such as the fire-affected apartment and the stairwell. Lethal concentrations of CO and CO2 were rapidly reached, severely impairing evacuation capability within the fire-affected apartment and the stairwell. Natural ventilation proved insufficient for controlling smoke and toxic gasses, highlighting the need for additional sealing measures and forced ventilation.

From the perspective of children and parents: What makes communal open spaces in multi-story residential neighborhoods child-friendly?

An increasing number of children live in apartments due to global trends in urbanization. However, little attention has been paid to the communal open spaces that are appropriate and attractive to children. This study aims to identify characteristics that significantly impact the quality of child-friendly communal open spaces within multi-story residential neighborhoods. The paper first reviewed the relevant literature to develop a conceptual framework. The measurements for the framework factors were then calculated through two online questionnaires seeking the perspectives of children and parents. Participants consist of 441 children aged 6–12 years and 576 parents. Both groups were living in 3 to 9-story residential buildings in Sanandaj, Iran. The findings show the four most significant factors for a child-friendly communal open space: “connection with nature”, “spatial flexibility”, “social networking”, and “safety/security”, in this order. Water play is the most significant indicator of child-friendliness followed by the provision of a variety of play equipment and natural environments. The most significant safety indicators for children are the availability of an outdoor shelter and soft surface materials. While children prefer free space for self-directed activities, parents ranked formal sports fields higher. We suggest biophilic design and participatory design that involves children and parents.

Seismic Collapse Risk Assessment and Fragility Analysis of Reinforced Masonry Core Walls with Boundary Elements Using the FEMA P695 Methodology

In the past, the primary objective of structural design codes was centred around ensuring human life safety, with a strong focus on preventing structural collapse. This approach predominantly relied on force- or strength-based criteria as the basis for design. Nevertheless, a notable shift has occurred recently, transitioning the design philosophy from 'strength' towards a 'performance'-based approach. This shift signifies a growing recognition that strength and performance are not identical. However, to adopt the performance-based seismic design approach, it is essential to develop precise models for estimating damage and potential losses associated with various seismic force-resisting systems (SFRSs). Fragility functions are widely interpreted among the most prevalent damage and loss models. They establish a crucial link between specific demand parameters and the likelihood of exceeding various damage states. Although reinforced masonry (RM) structures have recently gained popularity, the seismic design of mid- to high-rise RM structures is still challenging because it requires a reliable SFRS capable of providing the needed ductility and capacity. Therefore, the main objective of this study is to evaluate the key seismic performance parameters (i.e., system overstrength and ductility) and to perform a collapse capacity risk assessment of reinforced masonry core walls with boundary elements (RMCW+BEs) as the main SFRS in RM structures. The current study utilizes the applied element method (AEM) implemented in the Extreme Loading for Structures software (ELS) to model three RM structures with various heights (10-, 15-, and 20-story buildings). Nonlinear pseudo- static pushover analysis was performed to quantify the ductility and overstrength of the proposed RM system following the FEMA P695 guidelines. In addition, an incremental dynamic analysis (IDA) was carried out to assess the seismic collapse risk of RMCW+BEs by generating system-level-based fragility curves. The results showed that the proposed RM system provides the needed ductility, overstrength and deformation capacity for a ductile SFRS for typical mid- and high-rise RM buildings. Furthermore, the developed collapse fragility curves verified excellent seismic performance, negligible collapse probability values and high reserved collapse capacity at the maximum considered earthquake (MCE) design level. The findings of this study significantly contribute toward adopting RMCW+BEs as an effective SFRS for typical RM buildings in the next generations of North American masonry design standards.

Performance-based seismic design of low-rise steel moment-resisting frames targeting collapse fragility curve

The aim of this study is to develop a performance-based seismic design method targeting a desirable collapse fragility curve. This direct fragility-based design method is developed and validated for low-rise steel moment-resisting frames. To this end, a relationship is first defined between target fragility curve and design displacement. To this end, 4-story buildings are designed with the design drift ratios of 1.5 % to 4 % and the seismic fragility analysis is performed via the Monte Carlo simulation. The mentioned relationship is derived by plotting the median collapse spectral acceleration versus the design drift ratio. With regard to have this relationship, a modified version of performance-based plastic design method is then proposed. The direct fragility-based design method has been proposed for the low-rise buildings located in Log Angeles. However, its efficiency is also validated for two other regions of Vancouver, Canada and San Francisco, U.S. It can be found from the results that the fragility curve of designed buildings is very close to the target fragility curves. Therefore, the direct fragility-based design method is capable of achieving a target fragility curve and can be considered as an effective design method for low-rise steel moment-resisting frames.

Poços de luz estão aptos a iluminar ambientes residenciais? Discussões normativas

Abstract Light wells in residential buildings represent a context that has received relatively little attention in daylighting analyses. This study aims to analyze the daylighting performance of a residential space with a window facing a light well, in order to contribute to the revision of NBR 15575:2013. The study conducted 1,152 daylighting analyses considering windows facing a light well, located on the first and fourth floors of a 4-story building. Clear and intermediate skies were considered in four Brazilian cities with different latitudes. Both the prescriptive method and point-in-time simulations were applied. The effectiveness of achieving daylit interior spaces through light wells strongly depends on the geometry of the light well and the external illuminance conditions of the city. Narrow light wells were found to be unsuitable for adequately daylighting the lower floor spaces. Furthermore, the prescriptive method was insufficient in representing daylighting originating solely from external wall interreflections. The study found that intermediate and superior performance levels, when achieved through point-in-time or spatial daylighting availability simulations, were never attained for the first-floor space. Therefore, the authors recommend that dense urban canyon situations and light wells be carefully considered in the revision of the standard.

Simplified design approach of a negative stiffness-based seismic base absorber via multi-objective optimization

In the field of seismic base absorption, the KDamper constitutes an innovative and effective vibration absorber, characterized by the incorporation of a negative stiffness element. Recent developments have introduced variants like the Extended KDamper (EKD) and the Seismic Base Absorber (SBA), elevating the performance and reliability of the original concept. However, the optimization of these devices relied exclusively on the application of the single-objective Harmony Search optimization algorithm. In this study, the EKD is optimized using the non-dominated sorting genetic algorithm type II (NSGA-II), which incorporates the crowding distance operator (CDO). The purpose of this multi-objective optimization is to explore the EKD’s full potential in simultaneously reducing the induced base displacements and superstructure’s dynamic responses. To simplify the design process and reduce computational complexity, a simplified design approach is introduced. According to this approach, the EKD device is integrated in the base of a single-degree-of-freedom (SDOF) system with a variable natural period, ranging from 0.1 s to 2.0 s (SDOF-EKD system), representing multi-story buildings that range from 1 to 20 stories. In addition, a scaling method is employed, using the SDOF-EKD optimization results to guide the design of EKD for multi-story buildings (MDOF-EKD systems), constituting an indirect optimization of these systems. A comparison is conducted between the generated Pareto fronts as emerged from the simplified design approach and those obtained by optimizing the EKD directly installed in the base of multi-story buildings. Furthermore, a numerical case study is performed in a 3-story benchmark building and the proposed optimized vibration control system is compared in terms of superstructure’s dynamic responses and base displacements with a conventional and a highly damped base isolated building of similar characteristics.

Seismic performance enhancement for low-rise and mid-rise steel frames using novel self-centering beam-to-brace links

This paper aims to propose a novel self-centering beam-to-brace link with examined Shape Memory Alloy (SMA) based apparatuses to improve the seismic resilience of steel frames. Based on the past experimental data, a three-dimensional computer model of the proposed link was established to simulate the nonlinear hysteretic behavior. The results showed that the proposed link could realize the perceived advantages. A simplified Finite Element (FE) model was developed and validated via the comparison with the computer model. A 3-story and a 9-story representative building were rehabilitated with the proposed link. The Nonlinear Response History Analyses (NRHAs) were conducted on the original and rehabilitated systems to evaluate their seismic performance comparatively. To achieve a fair comparison, the original and rehabilitated systems had the proximate vibration periods and the same flexural strength under a roof drift ratio of 2 %. Compared with the original systems, the corresponding rehabilitated systems exhibited equivalent performance of transient inter-story displacement, significant advantages in eliminating residual deformation, and slight disadvantages in limiting floor acceleration. A comprehensive measure was developed and revealed the rehabilitated systems achieved superior seismic overall performance compared to the original systems.

Seismic collapse risk assessment and fragility analysis of reinforced masonry core walls with boundary elements using the FEMA P695 methodology

In the past, the primary objective of structural design codes was centred around ensuring human life safety, with a strong focus on preventing structural collapse. This approach predominantly relied on force- or strength-based criteria as the basis for design. Nevertheless, a notable shift has occurred recently, transitioning the design philosophy from 'strength' towards a 'performance'-based approach. This shift signifies a growing recognition that strength and performance are not identical. However, to adopt the performance-based seismic design approach, it is essential to develop precise models for estimating damage and potential losses associated with various seismic force-resisting systems (SFRSs). Fragility functions are widely interpreted among the most prevalent damage and loss models. They establish a crucial link between specific demand parameters and the likelihood of exceeding various damage states. Although reinforced masonry (RM) structures have recently gained popularity, the seismic design of mid-to high-rise RM structures is still challenging because it requires a reliable SFRS capable of providing the needed ductility and capacity. Therefore, the main objective of this study is to evaluate the key seismic performance parameters (i.e., system overstrength and ductility) and to perform a collapse capacity risk assessment of reinforced masonry core walls with boundary elements (RMCW + BEs) as the main SFRS in RM structures. The current study utilizes the applied element method (AEM) implemented in the Extreme Loading for Structures software (ELS) to model three RM structures with various heights (10-, 15-, and 20-story buildings). Nonlinear pseudo-static pushover analysis was performed to quantify the ductility and overstrength of the proposed RM system following the FEMA P695 guidelines. In addition, an incremental dynamic analysis (IDA) was carried out to assess the seismic collapse risk of RMCW + BEs by generating system-level-based fragility curves. The results showed that the proposed RM system provides the needed ductility, overstrength and deformation capacity for a ductile SFRS for typical mid- and high-rise RM buildings. Furthermore, the developed collapse fragility curves verified excellent seismic performance, negligible collapse probability values and high reserved collapse capacity at the maximum considered earthquake (MCE) design level. The findings of this study significantly contribute toward adopting RMCW + BEs as an effective SFRS for typical RM buildings in the next generations of North American masonry design standards.

Diseño y análisis dinámico de un edificio multifamiliar de 4 niveles sin sótano en la Provincia de Chanchamayo

In the present investigation, the design of a 4-story building without a basement located in the Province of Chanchamayo of Peru was carried out, intended for a multi-family home made up of structural elements such as columns, beams, and plates, which each one was designed and modeled under the Peruvian Load Regulations E. 020, Earthquake-resistant Design E. 030, Reinforced Concrete E. 060, Masonry E. 070 and General Design Conditions A. 010. The use of these Standards is established in the National Building Regulations that allowed compliance with the objective of designing and carrying out the Dynamic Analysis of the Building under the Earthquake methodology, which is based on the Load factor and resistance design method. Modeling was carried out with the help of ETABS software to obtain results necessary for the design and analysis of the structure. Finally, it was obtained that the building will use the structural system for structural walls, which has a basic reduction coefficient equal to 6 and it is concluded that the methodology used allows guaranteeing the safety, functionality and quality service of a building.

Analysis and Optimization of Tuned Mass Dampers for Seismic Resilience in 5- to 20-story Buildings

Analysis and Optimization of Tuned Mass Dampers for Seismic Resilience in 5- to 20-story Buildings

Pressurization System under Various Operating Conditions for Smoke Control

The importance of smoke control systems has been emphasized for a safe evacuation and efficient firefighting activities during fire situations. To protect stairwells from smoke hazards, ‘Design Guide for Smoke Control System of Special Evacuation Stairwell and Lobby (NFPC501A)’ has been presented. In domestic area, pressurization systems utilize an air supply system consisting of fans, ducts, and dampers for supplying the outdoor air to the lobbies . For a 10-story model building, the design of the pressurization system must consider the leakage/supply flow rate, pressure loss, and fan performance. In this study, the flow field of the pressurization system under various operating conditions was analyzed using CONTAM network model.